Configure the Encapsulation on a Logical Interface

Generally, you configure an interface's encapsulation at the [edit interfaces interface-name] hierarchy level. However, for some encapsulation types, such as Frame Relay, ATM, and Ethernet VLAN encapsulations, you can also configure the encapsulation type that is used inside the Frame Relay, ATM, or VLAN circuit itself. To do this, include the encapsulation statement at the [edit interfaces interface-name unit logical-unit-number] hierarchy level:

[edit interfaces interface-name unit logical-unit-number] 

encapsulation (atm-ccc-cell-relay | atm-ccc-vc-mux | atm-tcc-vc-mux | atm-cisco-nlpid | atm-nlpid | 
atm-snap | atm-tcc-snap | atm-vc-mux | ether-over-atm-llc | frame-relay-ccc | frame-relay-tcc | 
multilink-ppp | multilink-frame-relay-end-to-end | vlan-ccc); 

Some of the ATM encapsulations are defined in RFC 1483, Multiprotocol Encapsulation over ATM Adaptation Layer 5.

With the atm-nlpid, atm-cisco-nlpid, and atm-vc-mux encapsulations, you can configure the family inet only. With the circuit cross-connect (CCC) circuit encapsulations, you cannot configure a family on the logical interface. A logical interface cannot have frame-relay-ccc encapsulation unless the physical device also has frame-relay-ccc encapsulation. A logical interface cannot have frame-relay-tcc encapsulation unless the physical device also has frame-relay-tcc encapsulation. In addition, you must assign this logical interface a DLCI in
the range 512 through 1022 and configure it as point-to-point.

For interfaces that carry IPv4 traffic, you can configure ether-over-atm-llc encapsulation. When you use ether-over-atm-llc encapsulation, you cannot configure multipoint interfaces.

A logical interface cannot have vlan-ccc encapsulation unless the physical device also has vlan-ccc encapsulation. For encapsulation type vlan-ccc, you must assign this logical interface a VLAN ID in the range 512 through 1023; if the VLAN ID is 511 or lower, it is subject to the normal destination filter lookups in addition to source address filtering.

For information about multilink encapsulations, see Configure Multilink and Link Services Logical Interface Encapsulation.

You can create an ATM cell relay circuit by configuring an entire ATM physical device or
an individual virtual circuit (VC). When you configure an entire device, only cell relay encapsulation is allowed on the logical interfaces; for ATM 1 PICs, you use the atm-options statement to control the number and location of VCs. Allowed VCs on ingress and egress ATM interfaces should be the same. For most interfaces, you can define a maximum of 4090 VCs per interface. The highest-numbered VC value you can configure is 4089. For ATM OC-3 interfaces, you can define a maximum of 8180 VCs per interface. For ATM OC-12 interfaces, you can define a maximum of 16,360 VCs per interface. Promiscuous mode removes these limits. For more information, see Configure ATM 1 and ATM 2 Cell-Relay Promiscuous Mode.

For ATM 1 interfaces, you can dedicate the entire device to a cell relay circuit by including the allow-any-vci statement under unit 0, as shown in the following example. Once you enter this statement, you cannot configure other logical interfaces in the same physical interface.

[edit interfaces at-1/2/0]

encapsulation atm-ccc-cell-relay;

atm-options {

    vpi 0 maximum-vcs 256;

}

unit 0 {

    point-to-point; 

    encapsulation atm-ccc-cell-relay;

    allow-any-vci;

}

Alternatively, to configure an individual VC on a specific logical interface, include a statement similar to the following example:

[edit interfaces at-1/1/0]

encapsulation atm-ccc-cell-relay;

atm-options {

    vpi 0 maximum-vcs 256;

}

unit 120 {

    encapsulation atm-ccc-cell-relay;

    vci 0.120;

}

 When you use ATM CCC cell relay encapsulation, you must configure both the physical and logical encapsulation with atm-ccc-cell-relay. You cannot mix different logical encapsulation types on an interface that you have configured with ATM CCC cell relay physical encapsulation.